The nation of  Antharia was beset with perennial locust plagues which were finally eliminated with Kovalli's secret insect-exterminations spells which were put in use after the tenth century Conference of Quendor saw the temporary unification of many kingdoms.

Swarms of bloodsucking locusts so thick as to blot out the sun like a black storm cloud, gather in the meadows to the west of Egreth Castle, where they pick adventurers clean to the bones.

SOURCE(S): Sorcerer, Zork IV:Conquest at Quendor